How Does Brain Structure Differ in People with Hair-Pulling Disorder?

What you need to know

This study used advanced brain imaging techniques to examine brain structure and connectivity in people with trichotillomania (hair-pulling disorder).
While overall brain network organization was similar between those with trichotillomania and healthy controls, some specific brain regions showed differences in connectivity.
Regions involved in sensory processing, motor control, and visual recognition had altered connectivity in trichotillomania, which may relate to symptoms of the disorder.

Background on trichotillomania

Trichotillomania, also known as hair-pulling disorder, is a mental health condition where a person repeatedly pulls out their own hair, resulting in hair loss. This behavior is difficult to control and can cause significant distress and problems in daily life. Trichotillomania affects about 1-2% of people at some point in their lives and is classified as an obsessive-compulsive related disorder.

While we know that trichotillomania involves difficulties with behavioral control, the exact brain mechanisms involved are not fully understood. Previous brain imaging studies have suggested that certain brain regions may function differently in people with trichotillomania, but findings have been somewhat limited and inconsistent. This study aimed to take a more comprehensive look at brain structure and connectivity in trichotillomania using advanced imaging techniques.

How the study was conducted

The researchers used magnetic resonance imaging (MRI) brain scans to examine brain structure in 23 adult women with trichotillomania and 16 healthy women without the disorder. They then used a technique called graph theoretical analysis to map out and analyze the structural networks and connections between different brain regions.

This allowed them to look at both the overall organization of brain networks as well as the connectivity of specific regions. They were particularly interested in identifying “hub” regions - areas of the brain that have a high number of connections and play an important role in coordinating brain activity.

Key findings on brain network organization

When looking at the overall organization of brain networks, the researchers found that people with trichotillomania and healthy controls had similar “small-world” properties. This refers to an efficient network organization that balances local connectivity within brain regions and long-range connectivity between distant regions.

Other measures of network integration and segregation were also similar between groups. This suggests that on a broad level, the basic organizational principles of brain networks are intact in trichotillomania.

Differences in specific brain regions

While overall network organization was similar, the study did find some notable differences when looking at the connectivity of specific brain regions:

Highly connected hub regions

In people with trichotillomania, the regions with the highest connectivity (hub regions) included:

Temporal lobe areas involved in sensory processing and object recognition
Parietal lobe areas involved in integrating sensory information
Occipital lobe areas involved in visual processing
Frontal lobe areas involved in behavioral control
Striatum, a deeper brain structure involved in motor control and habit formation

In contrast, the hub regions in healthy controls were primarily located in different parts of the frontal, parietal and temporal lobes.

Inferior temporal gyrus

The inferior temporal gyrus, a region involved in visual recognition and processing, showed significantly higher connectivity in people with trichotillomania compared to controls. This was true both when looking at its overall connectivity in the brain network and its local connections to nearby regions.

Pericalcarine cortex

The pericalcarine cortex, located in the occipital lobe and involved in early visual processing, showed lower connectivity in people with trichotillomania compared to controls.

What do these findings mean?

The differences in connectivity of specific brain regions in trichotillomania may provide clues about the neural basis of the disorder:

Altered connectivity in sensory and motor regions could relate to the sensory experiences (e.g. feeling of satisfaction) and motor behaviors (repeated hair-pulling) involved in trichotillomania.
Changes in visual processing areas may reflect differences in how visual information about hair or the body is perceived and processed.
Higher connectivity of the inferior temporal gyrus, involved in object recognition, could potentially relate to an excessive focus on or preoccupation with hair.
Involvement of frontal and striatal regions aligns with the idea that trichotillomania involves difficulties with behavioral control and habit formation.

Interestingly, some of the brain regions showing differences overlap with areas implicated in obsessive-compulsive disorder (OCD). This fits with the classification of trichotillomania as an obsessive-compulsive related disorder and suggests there may be some shared brain mechanisms.

Limitations and future directions

It’s important to note that this study was relatively small and only included adult women. Larger studies including men and people of different ages are needed to confirm and expand on these findings. Additionally, this study looked at brain structure, but future research examining brain function and activity could provide complementary insights.

Conclusions

While overall brain network organization appears intact in trichotillomania, there are differences in the connectivity of specific brain regions involved in sensory processing, motor control, and visual recognition.
These differences in brain connectivity may relate to core symptoms and behaviors in trichotillomania.
The findings partially overlap with brain differences seen in OCD, supporting the relationship between these conditions.
Further research is needed to fully understand how these brain differences contribute to trichotillomania and to determine if they could inform new treatment approaches.